Subversion Repositories fpga-cf

//------------------------------------------------------------------------------
// Title      : CDC Sync Block
// Project    : Virtex-4 Embedded Tri-Mode Ethernet MAC Wrapper
// File       : sync_block.v
// Version    : 4.8
//-----------------------------------------------------------------------------
//
// (c) Copyright 2004-2010 Xilinx, Inc. All rights reserved.
//
// This file contains confidential and proprietary information
// of Xilinx, Inc. and is protected under U.S. and
// international copyright and other intellectual property
// laws.
//
// DISCLAIMER
// This disclaimer is not a license and does not grant any
// rights to the materials distributed herewith. Except as
// otherwise provided in a valid license issued to you by
// Xilinx, and to the maximum extent permitted by applicable
// law: (1) THESE MATERIALS ARE MADE AVAILABLE "AS IS" AND
// WITH ALL FAULTS, AND XILINX HEREBY DISCLAIMS ALL WARRANTIES
// AND CONDITIONS, EXPRESS, IMPLIED, OR STATUTORY, INCLUDING
// BUT NOT LIMITED TO WARRANTIES OF MERCHANTABILITY, NON-
// INFRINGEMENT, OR FITNESS FOR ANY PARTICULAR PURPOSE; and
// (2) Xilinx shall not be liable (whether in contract or tort,
// including negligence, or under any other theory of
// liability) for any loss or damage of any kind or nature
// related to, arising under or in connection with these
// materials, including for any direct, or any indirect,
// special, incidental, or consequential loss or damage
// (including loss of data, profits, goodwill, or any type of
// loss or damage suffered as a result of any action brought
// by a third party) even if such damage or loss was
// reasonably foreseeable or Xilinx had been advised of the
// possibility of the same.
//
// CRITICAL APPLICATIONS
// Xilinx products are not designed or intended to be fail-
// safe, or for use in any application requiring fail-safe
// performance, such as life-support or safety devices or
// systems, Class III medical devices, nuclear facilities,
// applications related to the deployment of airbags, or any
// other applications that could lead to death, personal
// injury, or severe property or environmental damage
// (individually and collectively, "Critical
// Applications"). Customer assumes the sole risk and
// liability of any use of Xilinx products in Critical
// Applications, subject only to applicable laws and
// regulations governing limitations on product liability.
//
// THIS COPYRIGHT NOTICE AND DISCLAIMER MUST BE RETAINED AS
// PART OF THIS FILE AT ALL TIMES.
//
//------------------------------------------------------------------------------
// Description: Used on signals crossing from one clock domain to
//              another, this is a flip-flop pair, with both flops
//              placed together with RLOCs into the same slice.  Thus
//              the routing delay between the two is minimum to safe-
//              guard against metastability issues.
//------------------------------------------------------------------------------
 
`timescale 1ps / 1ps
 
module sync_block #(
  parameter INITIALISE = 2'b00
)
(
  input        clk,              // clock to be sync'ed to
  input        data_in,          // Data to be 'synced'
  output       data_out          // synced data
);
 
  // Internal Signals
  wire data_sync1;
  wire data_sync2;
 
 
  (* ASYNC_REG = "TRUE", RLOC = "X0Y0" *)
  FD #(
    .INIT (INITIALISE[0])
  ) data_sync (
    .C  (clk),
    .D  (data_in),
    .Q  (data_sync1)
  );
 
 
  (* RLOC = "X0Y0" *)
  FD #(
   .INIT (INITIALISE[1])
  ) data_sync_reg (
  .C  (clk),
  .D  (data_sync1),
  .Q  (data_sync2)
  );
 
 
  assign data_out = data_sync2;
 
 
endmodule